Replaced my upstream O2 sensors about 500 miles ago. Truck had 117,000 miles, and I am pretty sure they were original. I was averaging 15mpg over the last few thousand miles. Since swapping the sensors, I am now averaging 15.5mpg. My average over the last 950+ gallons of fuel is 14.9mpg. Before I did anything to the truck it wouldn’t get anything better than 13mpg.
The truck is running very well now. All the issues I was having with random stalling and idle dips are gone. What I have noticed since changing the O2 sensors is that the idle response to load changes is almost instantaneous vs. before when it would stumble when the a/c compressor kicked on, or I would go from drive to reverse, or turn the steering wheel while on the brakes.
So, if I were to recommend solutions to drivability problems they would be as follows:
-Canister Purge Valve
-Spark Plugs (all 16) and wires (check the pellets in the coils)
-Upstream O2 sensors
-Reset BMS if battery has been changed.
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